The company behind one of Australia's largest coal mines will proceed with its plans to build the mine despite a legal challenge against its approval.

Whitehaven Coal has announced to the Australian Securities Exchange it will go ahead with the construction of the $767 million open-cut Maules Creek mine in the Gunnedah Basin in north-western New South Wales.

The company says legal action launched by the Northern Inland Council for the Environment does not stop it from relying on the approval granted by the Federal Government in February.

The council has commenced legal proceedings in the Federal Court against former Federal Environment Minister Tony Burke and Whitehaven Coal, challenging the validity of the approval process.

It has also launched action against the expansion of the nearby Boggabri coal mine owned by the Japanese firm Idemitsu.

Council spokesman Phil Spark says the Maules Creek and Boggabri mines will require thousand of hectares of land clearing.

"The forest is mature, dominated by big old trees full of hollows and there's a lot of threatened species that occur," Mr Spark said.

"And all those threatened species and the critically endangered ecological communities will decline as a result of turning the forest into an open cut coal mine."

Whitehaven defended the approval process for Maules Creek as "comprehensive", and said the court would not be determining whether the project should have been approved.

"If, however, the court was to find that there was any legal error in the minister's granting of the approval on 11 February 2013, the company will request that the minister promptly cure the error, re-determine the application and grant a new approval," Whitehaven said.

Whitehaven says it wants the litigation to be resolved as soon as possible and will ask the court to expedite the hearing.

Whitehaven owns 75 per cent of the mine, with Japanese companies Itochu and J-Power holding the remainder.